Process for treating a metallic body with vapor-deposited treatment layer(s) and adhesion-promoting layer

ABSTRACT

This invention relates to a metal body having at least one vapor-deposited treatment layer overlying and adhered to at least one side of the metal body, and a layer of adhesion-promoting material overlying and adhered to at least one treatment layer, provided that when two treatment layers are deposited on one side of the body and the first layer is vapor-deposited zinc, the second layer is not vapor-deposited silica or alumina, said adhesion-promoting material being suitable for enhancing adhesion between said body and another substrate. The invention also relates to laminates comprising metal foils and at least one vapor-deposited treatment layer overlying and adhered to at least one side of the metal foil; a layer of adhesion-promoting material overlying and adhered to at least one vapor-deposited treatment layer; and a layer of an electrically non-conductive material overlying and adhered to the adhesion-promoting layer.

This is a division of application Ser. No. 08/713,100, filed Sep. 16,1996 now U.S. Pat. No. 5,709,956 and a con. of Ser. No. 08/232,820 Apr.22, 1994, now abandoned.

TECHNICAL FIELD

This invention relates to metallic bodies, and more particularly, tometal foils such as copper foils. The metal bodies have at least onevapor-deposited treatment layer overlying at least one side thereof, anda layer of an adhesion-promoting material overlying at least onetreatment layer. These foils are useful in the manufacture of a varietyof products including batteries, EMI/RFI shielding gaskets and panels,and printed circuit boards (PCBs).

BACKGROUND OF THE INVENTION

The present invention relates to the surface treatment of metal bodies,and more particularly, to metal foils such as copper foils which areused in the production of a variety of products including printedcircuit boards. More particularly, the invention relates to surfacetreatments for improving the properties of metallic bodies such ascopper foils to maintain a bright copper tone during long storage andthroughout lamination procedures conducted under heat and pressure whileat the same time retaining the solderability and/or solder-wettabilityof the surface of the copper foil.

Printed circuit boards are currently used as the substrate materials ina wide variety of electronic devices. Typically, these boards arefabricated from a thin sheet of copper foil laminated to either afiberglass/epoxy hard board or, in some instances, flexible plasticsubstrates. During the latter stages of the fabrication, the copper foilis printed with the necessary circuit pattern, and the unnecessaryportions of the copper foil are then etched away to provide the desiredinterconnecting circuitry between various components in the electroniccircuit design.

Copper foils used in such applications are prepared generally either byelectrolytic deposition or a rolling technique. When the copper foil isproduced electrolytically, the copper foil contains a matte or roughside and a shiny side. The side laminated to the plastic substratesgenerally is the matte side. Whether electrolytically formed copper foilor rolled copper foil is used, the surface of the foils thus formed arenot readily amenable to the production of adequate bond strength afterlamination. Therefore, the foil must be treated by additional chemicalprocesses to improve its properties including bondability to resinsurfaces, oxidation-resistance, corrosion-resistance, etc. The shinyside of the copper foils are treated to prevent oxidation during storageor lamination under heat and pressure. Various techniques have beensuggested and utilized to improve the adhesion of the matte side of thecopper foil to various polymeric substrates. One such practice forachieving adhesion between copper foil and insulating polymericsubstrates has been to roughen the copper surface.

Surface roughening has been achieved by several means. Theelectrodeposited copper foils can be electroformed with a rough surface.On top of this rough surface further roughening is carried out byapplying a high surface area treatment. These treatments may be a copperdeposited electrolytically in nodular or powder form, or a copper oxidewhich grows nodular or dendritic, among others. Often times the rolledcopper foil has mechanical roughness imparted to it during rolling or bysubsequent abrasion. The rolled foils also are conventionally treatedwith surface area increasing nodular copper or copper oxide treatments.

These surface roughening treatments increase adhesion to the polymers byforming a mechanical interlock with the resin. The mechanical interlockis formed when an adhesive in its liquid state is applied and then curedor when the resin melts and flows prior to cure during lamination. Thepolymers flow around the roughened surface area treatments to form themechanical interlock.

There are several factors contributing to the adhesion measured betweenthe copper foil and the polymeric resin. Some of these are surface area,type of roughness, wettability, chemical bond formation, type ofchemical bond, formation of interpenetrating networks, and properties ofthe adhering materials.

During an adhesion test the interlocked resin and copper often adherewell enough that failure occurs within the resin, a cohesive failure.With some resins the mechanical interlocking of treatment and resin doesnot result in the desired high adhesion and failure occurs at theinterface between resin and copper, an adhesive failure.

The surface roughening that has been used to enhance adhesion betweencopper and polymeric resin substrates may cause difficulties in themanufacture of PCBs and contribute to poor PCB performance. In thesubtractive copper etching process additional etching time is requiredto remove the dendrites or nodules embedded in the resin. This not onlyslows down the production process but contributes to greater line lossdue to the lateral etching of the copper line's sidewalls. The surfaceroughening contributes to poor PCB electrical performance by degradinghigh frequency electrical signals. The necessity of having a rough basefoil has limited other properties, such as tensile strength andelongation, that produce good laminate and PCB performance. Thedendritic or nodular surface roughening treatments are difficult toapply, requiring special equipment in the case of electrolytictreatment, and special chemicals in the case of the oxide treatments.

The bonding strength of the foils to the polymeric substrates can alsobe improved by coating the foils with materials which are capable ofenhancing the adhesion between the foil and the polymeric substrates.Various materials have been suggested in the literature asadhesion-promoting compounds, and these include organic materials suchas phenol resins, epoxy resins, urethanes, silanes, polyvinyl butyralresins, etc. It also has been suggested to deposit layers of variousmetals and metal alloys to improve the adhesion between the copper foiland the polymeric substrates.

U.S. Pat. No. 3,585,010 (Luce et al) describes a conductive element fora printed circuit board comprising a copper foil and a metallic barrierlayer which substantially reduces the staining of printed circuitboards. The metallic layer is a thin deposit of a metal selected fromthe group consisting of zinc, indium, nickel, cobalt, tin, brass andbronze. The barrier layer is applied to one side of the copper foil bystandard electrodeposition procedures pertaining the particular metalliclayer. The patentees also suggest that the metallic barrier layer doesnot have to be electrodeposited on the surface of the copper foil butmay be applied by other means such as vapor deposition. After depositionof the barrier layer, the foil may be given additional treatments priorto lamination such as with a corrosion-inhibiting agent.

U.S. Pat. No. 4,268,541 (Ikeda et al) describes a process for producinga material having a vapor-deposited metal layer useful particularly informing recording materials. The process described in this patentcomprises vapor depositing a layer of metal, a layer of different metalsin contact with each other, a layer of a metal alloy, a layer of a metaland a metal compound in contact with each other or a layer of a metalcompound as the metallic layer on a support or substrate which may be apolymeric material, a composite of a polymeric material and paper, wovenor non-woven cloth or paper. Subsequent to the formation of a layer byvapor deposition, a second layer of an organic material is applied overthe metallic layer by vapor deposition using an evaporable organicmaterial. The layer of organic compound over the metal layer serves as abuffering layer for the metallic layer and renders the metallic layerformed by vapor deposition more slippable.

U.S. Pat. No. 4,383,003 (Lifshin et al) and its divisional U.S. Pat. No.4,455,181 describe copper-clad laminates useful in preparing highresolution printed circuit patterns. Laminates are made by vapordepositing a film of zinc on a vapor-deposited copper film which is on asilica-coated aluminum carrier sheet, vapor depositing a silica film onthe resulting zinc-copper foil, bonding the resulting body to asubstrate, and then stripping the silica-coated aluminum carrier sheetfrom the copper clad laminate. One of the laminated products describedin the '003 patent comprises a thin copper sheet, an ultra-thin film ofzinc vapor-deposited on said copper sheet and a film of silica oralumina vapor-deposited on said zinc film. Optionally, a coating of asilane coupling agent is deposited over the silica film.

SUMMARY OF THE INVENTION

This invention relates to a metal body having at least onevapor-deposited treatment layer overlying and adhered to at least oneside of the metal body, and a layer of adhesion-promoting materialoverlying and adhered to at least one treatment layer, provided thatwhen two treatment layers are deposited on one side of the body and thefirst layer is vapor-deposited zinc, the second layer is notvapor-deposited silica or alumina, said adhesion-promoting materialbeing suitable for enhancing adhesion between said body and anothersubstrate. The invention also relates to laminates comprising: a metalfoil and at least one vapor-deposited treatment layer overlying andadhered to at least one side of the metal foil; a layer ofadhesion-promoting material overlying and adhered to the at least onevapor-deposited treatment layer; and a layer of an electricallynon-conductive material overlying and adhered to the adhesion-promotinglayer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram representing a cross-sectional view of ametal foil of the present invention including one vapor-deposited layerand one adhesion-promoter layer.

FIG. 2 is a schematic diagram representing a cross-sectional view ofanother metal foil of the present invention.

FIG. 3 is a schematic diagram representing a cross-sectional view ofanother metal foil according to the present invention.

FIG. 4 is a schematic diagram representing a cross-sectional view ofanother metal foil according to the present invention.

FIG. 5 is a schematic diagram representing a cross-sectional view ofanother metal foil according to the present invention.

FIG. 6 is a schematic diagram representing a cross-sectional view ofanother metal foil according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Metal Bodies

The metal bodies which can be utilized and treated in accordance withthe present invention are preferably electrically conductive metalbodies. The choice of metal body will depend upon the desired end use ofthe metal body.

The metal bodies utilized in the present invention may be of anyconfiguration such as metal sheets, bars, rods, wires, foils, etc.Preferably, the metal body is a foil, more particularly, a copper orcopper-based alloy foil. Accordingly, the discussion within thespecification generally will be directed to foils, and moreparticularly, copper foils, although the general discussion should beunderstood to be applicable to other foils and metal bodies.

Copper and copper-based alloy foils are well known in the art and aremade by various techniques. Wrought or rolled foil is produced bymechanically reducing the thickness of a metal (copper) or alloy (copperalloy) strip or ingot by a process such as rolling. Electrodepositedfoil is produced by electrolytically depositing copper ions on arotating cathode drum and then peeling the deposited strip from thecathode. This procedure can be used to form continuous strips of thefoil. Foils can also be prepared by other procedures. For example, acopper foil can be prepared by electrodepositing or vapor depositing alayer of copper on a conductive carrier such as aluminum. Another copperfoil can be prepared by rolling a copper layer onto an alloy foil suchas an iron-nickel alloy. The copper can be rolled onto one or both sidesof the iron-nickel alloy. Yet another example of a multilayer foil is amolybdenum foil or layer coated on both sides with copper.Alternatively, copper can be vapor-deposited on a release coatedcarrier, and thereafter the vapor-deposited film of copper can beremoved from the release-coated carrier.

Electrodeposited and rolled or wrought copper foils are preferred, andelectrodeposited copper foils are especially preferred. The copper foilstypically have nominal thicknesses ranging from about 0.0002 inch toabout 0.02 inch. Foil thickness is sometimes expressed in terms weightand typically the foils of the present invention have weights orthicknesses ranging from about ⅛ to about 14 oz/ft². The foils used asthe base foil in this invention may be as-plated foils or annealedelectrodeposited foils. The wrought copper foils may be as-rolled orannealed wrought copper foils.

Electrodeposited copper foils have a smooth or shiny (drum) side and arough or matte (copper deposit growth front) side. The treatment layersdescribed more fully below can be adhered to either side of the foil andin some instances are adhered to both sides.

In one embodiment, the side or sides of the foil (electrodeposited orwrought) to which the treatment layer is adhered is a “standard-profilesurface,” “low-profile surface” or “very-low-profile surface.” The term“standard-profile surface” is used herein to refer to a foil surfacehaving an R_(tm) of about 10 μm or less. Standard profileelectrodeposited copper foil also may be characterized as having acolumnar grain structure of preferred orientation and high densities ofcrystal defects such as discolorations and twin boundaries, and the foilhas an average grain size of up to about 20 microns. The term“low-profile surface” refers to a foil surface having an R_(tm) of about7 μm or less. The term “very-low-profile surface” refers to a foilsurface having an R_(tm) of about 4 μm or less. R_(tm) is the mean ofthe maximum peak-to-valley vertical measurement from each of fiveconsecutive sampling measurements, and can be measured using aSurftronic 3 profilometer marketed by Rank Taylor Hobson, Ltd.,Leicester, England.

When the copper foil products of the present invention are to be used inPCB applications, it is often desirable that the copper foils havecontrolled low profiles to provide etchability and impedance control. Itis also preferred that these foils have high ultimate tensile strengths(UTS) to provide desired handling and surface quality characteristics,and high elongations at elevated temperatures to resist cracking. In oneembodiment, the copper foils utilized in the present invention arecharacterized as being controlled low profile electrodeposited copperfoils having a substantially uniform randomly oriented grain structurethat is essentially columnar grain-free and twin-boundary-free and hasan average grain size of up to about 10 microns. These foils generallyhave ultimate tensile strength measured at 23° C. in the range of about70,000 to about 120,000 psi and an elongation measured at 180° C. ofabout 6% to about 28%. Copper foils having these characteristics may beprepared by the process which comprises (A) flowing an electrolytesolution between an anode and a cathode and applying an effective amountof voltage across said anode and said cathode to deposit copper on saidcathode; said electrolyte solution comprising copper ions, sulfate ions,and at least one organic additive or derivative thereof, and the currentdensity being in the range of about 0.1 to about 5 A/cm²; and (B)removing the copper foil from said cathode. In one embodiment, thechloride ion concentration of said solution is up to about 1 ppm.

Such copper foils generally have a matte-side raw foil roughness(R_(tm)) of 1 to about 10 microns. The R_(tm) for the shiny side ofthese foils is preferably less than about 6 microns, and more often inthe range of from about 2 to about 5 microns. The weights for thesecopper foils generally are in the range of from about ⅛ to about 14ounces per square foot. The foil having a weight of 0.5 ounce per squarefoot has a nominal thickness of about 17 microns.

The terms “untreated” and “raw” are used herein to refer to a base foilas prepared which has not been subjected to subsequent treatment, (e.g.,one or more surface roughening treatments) for the purpose of refiningor enhancing the foil properties. The raw foil is also referred to as“as plated” or “as rolled.” The term “treated” as used herein is usedherein to refer to raw or base foil that has been subjected to at leastone such treatment. These treatments are conventional and typicallyinvolve the use of various treating and rinsing solutions. Either orboth sides of the foil can be treated. The treatments may be chemical orphysical treatments.

Various chemicals can be applied to the raw foil to improve thecharacteristics of the foil surface. For example, the foil surfaces canbe contacted with an acid such as sulfuric acid to effect microetchingof the surface. Also prior to application of the vapor-depositedtreatment layers in accordance with the present invention, the copperfoils may be electrolytically provided with various metal coatings suchas zinc, tin, copper, chromium or alloys thereof (e.g., chromium-zinc)by dipping and electroplating techniques well known to those skilled inthe art. For example, the electroplating of tin or a tin-zinc alloy onthe shiny side of a copper foil is described in U.S. Pat. No. 4,082,591which is hereby incorporated by reference. In another example, the rawfoil is dipped in an acid solution of chromic acid (CrO₃) to deposit achromium coating.

Although the foils can be subjected to a surface roughening treatmentprior to the application of at least one vapor-deposited treatmentlayer, it is a significant advantage of the invention that improvedadhesive characteristics for the foil can be achieved without subjectingthe foil to an added surface roughening treatment. Thus, in oneembodiment of the invention, the foil used in the invention can be rawfoil which has been cleaned of surface impurities but is otherwisecharacterized by the absence of any added surface roughening treatmenton the side or sides to which the vapor-deposited treatment layer(s) isadhered. The term “added surface roughening treatment” refers to anytreatment performed on a base or raw foil that increases the roughnessof the surface of the foil. These treatments include chemical treatmentssuch as copper deposited electrolytically in nodular or powder form, orcopper oxide which grows nodular or dendritic. In one preferredembodiment, the base foil is microetched by dipping in an acid solutionsuch as a 20% by volume of sulfuric acid in water at about 65° C. forabout 15 seconds followed by an immediate water rinse. Other usefulsurface modification treatments include glow discharge and sputtering.

In one embodiment, the mechanical roughness imparted to wrought copperfoil during rolling or by subsequent abrasion which increases roughnessbeyond that of a standard profile surface is considered to be an addedsurface roughening treatment. In another embodiment, any roughnessimparted to the raw or base copper foil that increases the roughness ofsaid foil beyond that of a standard profile surface is considered to bean added surface roughening treatment. In another embodiment, anyroughness imparted to the raw or base copper foil that increases theroughness of said foil beyond that of a low-profile surface isconsidered an added surface roughening treatment. In another embodiment,any roughness imparted to the raw or base copper foil that increases theroughness of said foil beyond that of a very low-profile surface isconsidered an added surface roughening treatment.

As indicated above, it is within the scope of the invention to apply thevapor-deposited treatment layer(s) to foils which have been subjected toan added surface roughening treatment the treatment. Thus, in oneembodiment, one or both sides of the foil may be treated to provide aroughened layer of copper or copper oxide prior to vapor deposition ofthe treatment layer or layers. The copper can be depositedelectrolytically in nodular or powder form by techniques well known tothose skilled in this art. The copper oxide can grow nodular ordendritic. In another embodiment, the side or sides of the base or rawfoil to which the vapor-deposited treatment layer is adhered isuntreated prior to the application of the vapor-deposited treatmentlayer to the foil.

Treatment Layer(s)

The metal bodies of the present invention have at least onevapor-deposited treatment layer overlying and adhered to at least oneside of the metal body. As noted above, the vapor-deposited treatmentlayer may be deposited over raw or untreated foil, or the treatmentlayers may be applied to the foil after the foil has been subjected toone or more added surface roughening treatments.

In one embodiment, one side of the foil has a treatment layer, and inanother embodiment, both sides of the foil have a treatment layer. In afurther embodiment of the invention, one or both sides of the foil mayhave two or more consecutive vapor-deposited treatment layers asdescribed more fully below. In yet another embodiment, the foils of thepresent invention have at least one roughened layer of copper or copperoxide between the raw or base foil and the vapor-deposited treatmentlayer or layers. In a further embodiment, the foils of the presentinvention may have at least one chemically or electrodeposited metal ormetal oxide layer on the foil and between the foil and the one or morevapor-deposited layers.

A variety of vapor-deposited treatment layers may be present on thefoils of the present invention to provide desirable and beneficialproperties to the foils such as stabilization layers, barrier layers, orcombinations thereof to prevent or minimize the appearance of stains andspottings throughout the resinous layer when the foils are used to formprinted circuitboards, oxidation-inhibiting layers, moisture-resistantlayers, etc.

In one preferred embodiment, the vapor-deposited treatment layer orlayers deposited on one or both sides of the foil is a metallic barrierlayer and/or a metallic stabilization layer. As noted, the inventioncontemplates the use of more than one such metallic layers on either orboth sides of the foil. The term “metallic” as applied to the metalliclayers useful in the present invention includes metals, alloys, as wellas metal compounds such as metal oxides or nitrides although metals arepreferred.

Examples of metals which may be included in the vapor-deposited metalliclayer include magnesium, aluminum, titanium, chromium, manganese,copper, bismuth, cobalt, nickel, zinc, indium, tin, molybdenum, silver,gold, tungsten, zirconium, antimony, chromium-zinc alloy, brass, bronze,and mixtures of two or more of said metals. When the metallic layers orlayers are deposited on the matte side of an electrodeposited copperfoil, the metal is preferably indium, tin, cobalt, nickel, zinc, copper,manganese, chromium, titanium, bismuth, bronze or zinc-chromium alloy.Preferred metals for the metal layer or layers applied to the shiny sideof an electrodeposited copper foil are those which are etchable andthese include indium, chromium, magnesium, aluminum, copper, tin,nickel, cobalt, zinc or zinc-chromium alloys.

The foils of the present invention also can contain two or morevapor-deposited layers on one or both sides of the foil. For example, afirst (a barrier layer) layer of any of the above-identified metals ormetal alloys can be vapor-deposited on the copper foil followed by thevapor deposition of a second layer (stabilization layer). Alternatively,the second layer may, for example, comprise a metal oxide such assilica, alumina, indium oxide, magnesium oxide, etc., provided that thesecond vapor-deposited layer does not contain vapor-deposited silica oralumina when the first vapor-deposited layer is zinc.

The thickness of the one or more treatment layers on the metal bodies ofthe present invention can be varied, and the desired thickness for anyparticular application can be readily determined by one skilled in theart. In general, when a treatment layer is a metallic layer, thethickness of the metallic layer may range from about 10 to about 10,000Å, and in some instances, will be within the range of from about 20 to1000 Å.

In another embodiment wherein a barrier layer of metal overlies and isadhered to the base foil, and a metal stabilization layer isvapor-deposited over the barrier layer, the thickness of the barrierlayer may range from about 0.01 to about 1 micron, and the thickness ofthe stabilization layer may vary from 0.002 to about 0.1 micron. Metalswhich are particularly useful in the stabilizer layer include tin,nickel, molybdenum, indium, magnesium, aluminum, Zn, Cr and Zn—Cralloys.

The vapor-deposited treatment layers can be obtained by vapor depositiontechniques well known to those skilled in the art, and such techniquesinclude physical vapor deposition (PVD) which includes thermalevaporation, electron beam deposition, inductive and/or resistivedeposition, ion plating, sputtering, plasma-activated evaporation,reactive evaporation, and activated reactive evaporation; and chemicalvapor deposition (CVD). Physical vapor deposition also has been referredto in the literature as vacuum metallization and evaporative coating. Inthermal evaporation deposition procedures, the material to be applied tothe metallic body (generally a metal or alloy) is heated in a highvacuum (e.g., 10⁻² to about 10⁻⁶ torr) whereupon the material evaporatesor sublimates and travels to the metal object to be coated. Insputtering processes, energetic inert ions created in a plasma dischargeimpact a target and cause the ejection of coating material throughmomentum exchange. Physical vapor deposition essentially involves thetransfer of the material and the formation of coatings by physical meansalone in contrast to chemical vapor deposition in which the materialtransfer is effected by chemical reactions induced by temperature orconcentration gradients between the substrate and the surroundinggaseous atmosphere. The principals of vapor deposition and proceduresuseful in vapor depositing various materials including metals isdescribed in Vapor Deposition, edited by C. F. Powell et al, John Wiley& Sons, Inc., New York, 1966.

Chemical vapor deposition usually is accomplished by vaporizing ametallic halide and decomposing or reacting the vapors at the foilsurface to yield the non-volatile metal on the surface of the foil as acoating. The chemical reactions of vapor deposition can be effected bythermal deposition or pyrolysis, hydrogen reduction, reduction withmetal vapors, reaction with the metal foil, chemical transportreactions, etc. These procedures are described in detail in Chapter 9 ofVapor Deposition, C. F. Powell, J. H. Oxley, and J. M. Blocker, Jr.,editors, J. Wiley & Sons, Inc., New York, 1966, and this chapter isincorporated by reference for its description of the CVD processes.

Copper foils having vapor-deposited treatment layers in accordance withthis invention, and in particular, vapor-deposited metallic layers, canbe obtained utilizing an apparatus available from Edwards CoatingSystems, identified as E306A. This unit has an operating vacuum range offrom 2×10⁻⁶ mbar to 2×10⁻⁵ mbar. Vapor deposition of metals cangenerally be accomplished in satisfactory thicknesses (e.g., about 10 Åto 3000 Å) in from about 0.3 to about 40 minutes or more at evaporatingcurrents of from 35 to 80 milliamps. The evaporating current useddepends on the amount and form of the material to be vaporized. Forexample, currents of about 65-80 milliamps generally are used tovapor-deposit indium, tin, chromium, cobalt and nickel. Evaporationcurrents in the range of 35-50 milliamps are satisfactory for magnesiumand zinc, and currents in the range of 50-65 are satisfactory fordepositions aluminum, manganese, tin and brass. In the Edwards apparatusthe distance from the boat containing the metal to be vaporized to thefoil sample is about 5 inches. In general, thin foil or chips of thecoating material are placed in a tungsten boat and heated under vacuum.

After the treatment layer has been vapor-deposited on the copper foil,it may be further treated to improve its properties prior to applicationof the adhesion-promoting layer. The vapor-deposited metallic layer canbe heated to an elevated temperature such as from about 80° C. to about800° C. (depending on the vapor-deposited metal) for a few seconds toone hour to modify the surface coverage, characteristics and propertiesof the metallic layer. For example, a metallic layer such as indiumdeposited on a copper foil which does not completely cover the copperfoil leaving about 2% to 3% or even 5% exposed copper. When thevapor-deposited indium coating is baked in an oven at an elevatedtemperature of about 190° C. for 60 minutes, the exposed copperconcentration of the surface decreases to as little as 0.5%. In anotherembodiment, the vapor-deposited metal is baked in an oven in anatmosphere of oxygen to convert at least some of the surface metal tothe oxide form. Exposure of the metal surface to nitrogen at an elevatedtemperature converts at least a portion of the surface metal to metalnitride. Heating of the vapor-deposited metal prior to application ofthe adhesion-promoting layer also accelerates the formation of an alloyof the base metal and the vapor-deposited metal at the basemetal-deposited metal interface.

The properties of the vapor-deposited metallic layer or layers presentin the metal foils of the present invention may be further modified byion-bombardment/heating, oxygen plasma ion bombardment, andelectroplating of the vapor-deposited metallic layer with materialswhich improve desirable properties such as providing oxidation andstabilization protection. For example, the vapor-deposited metal layermay be electrochemically treated with acidic solutions containing, forexample, chromium, copper, tin, bismuth, or zinc-chromium mixtures,etc., to deposit chromium, tin, bismuth or zinc-chromium coatings overthe vapor-deposited metal coating to improve properties such asoxidation resistance, etc., prior to application of theadhesion-promoting layer.

Adhesion-Promoting Layer

At least one surface or side of the metal bodies of the presentinvention have at least one vapor-deposited treatment layer as describedabove, and at least one of the treatment layers has anadhesion-promoting layer overlying and adhered to the treatment layer.The adhesion-promoting layer is adapted for enhancing the adhesionbetween the foil and a substrate such as a polymeric resin substrateused in the formation of PCBs. Depending on the nature of the adhesiveor adhesion-promoter and the intended use of the adhesive layer coatedfoil, the thickness of this layer may vary over a wide range from about4 to about 500,000 Å. A wide variety of adhesion-promoting materials areknown in the art for improving the adhesion of treated and untreatedmetal foils to other substrates including polymeric resin substrates,and such conventional adhesives can be utilized in the presentinvention. Improved adhesion is obtained as a result of the coactionbetween the adhesive and the vapor-deposited treatment surface orsurfaces which have been previously applied to the metal foil. Forelectrical purposes, high dielectric strength adhesives are selected.The adhesives or adhesion-promoters may be organic, organometallic orinorganic compounds.

In one embodiment, the adhesion-promoting material is an organicmaterial which may comprise thermosetting or thermoplastic polymers andcopolymers, and mixtures thereof. When organic materials such asthermosetting or thermoplastic polymers and copolymers are used, theyare often referred to in the art as adhesives, and the thickness of thelayer is at the higher end of the range given above. Generally,thicknesses of from about 10,000 Å up to about 500,000 Å are appliedover the vapor-deposited treatment layer. In contrast, theorganometallic compounds useful in the adhesion-promoting layer such asthe silane coupling agents are generally referred to as adhesionpromoters, and the thickness of the adhesion promoter is much less,e.g., from about 4 Å to about 200 Å.

Examples of thermosetting and thermoplastic polymers and copolymersinclude epoxy resins, formaldehyde resins, phenol formaldehyde resins,polyester resins, butadiene and acrylonitrile rubbers, polyvinylbutyralresins, etc. Mixed poly(vinylbutyral)-phenol-formaldehyde resins alsoare useful. Various alkyd resins which are polyesters may be used asadhesive. An example of a useful alkyd resin is a maleicanhydride-ethylene glycol polyester. Such polyesters may be dissolved instyrene and copolymerized in place under heat with the addition of asmall amount of a peroxide initiator to provide excellent adhesives.

In one embodiment, the adhesive material used to form theadhesion-promoting layer comprises (A) at least one multi-functionalepoxy resin. In another embodiment the adhesion-promoting layercomprises a mixture of epoxy resins comprising (A) at least onemultifunctional epoxy resin; and (B) a composition derived from (B-1) atleast one difunctional epoxy resin; and (B-2) at least one componentrepresented by the formula:

R-(G)_(n)  (I)

wherein in Formula I, R is an aromatic, alicyclic or heterocyclic group;G is a functional group selected from the group consisting of COOH,OHSHNH₂NHR¹, (NHC(═NH))_(m)NH₂, R²COOH, R²OH, R²SH, R²NH₂ and R²NHR¹,wherein R¹ is a hydrocarbon, R² is an alkylene or alkylidene group, andm is a number in the range of from 1 to about 4; and n is a numberranging from 3 up to the number of displaceable hydrogens on R.

The multifunctional epoxy compounds (A) which can be used alone or incombination with (B) are those containing an average of more than twoepoxy groups (oxirane rings) per molecule. In one embodiment theseepoxies contain an average of up to about six epoxy groups per molecule.In one embodiment the multifunctional epoxy is an epoxy novolac resin.The multifunctional epoxy can be a trifunctional or tetrafunctionalepoxy resin. (A trifunctional epoxy resin is an epoxy resin thatcontains an average of three epoxy groups per molecule, and atetrafunctional epoxy resin contains an average of four epoxy groups permolecule.) The multifunctional epoxies typically have average epoxyequivalent weights in the range of about 100 to about 250, and in oneembodiment from about 190 to about 240. (An epoxy equivalent weight isthe molecular weight of the epoxy molecule divided by the number ofepoxy groups in the molecule. Thus, for example, a trifunctional epoxyhaving a molecular weight of 600 would have an epoxy equivalent weightof 200.)

Examples of commercially available trifunctional epoxy resins that areuseful include Tactix 742 (Dow Chemical) and PT 810 (Ciba Geigy).Examples of commercially available tetrafunctional epoxy resins that areuseful include MT 0163 (Ciba Geigy), Epon 1031 (Shell) and Epon HPT 1071(Shell).

The epoxy novolacs that are useful include the epoxy cresols and theepoxy phenol novolacs, Examples of commercially available novolacs thatare useful include DEN 438, DEN 439 and Tactix 785 (each of which isavailable from Dow), DPS 164 (Shell) and ECN 1299 (Ciba Geigy).

The difunctional epoxy resin (B-1) can be any difunctional epoxy resinhaving an average molecular weight in the range of about 1000 to about10,000 (epoxy equivalent weight of about 500 to about 5000), and in oneembodiment an average molecular weight of about 1000 to about 6000. (Adifunctional epoxy resin is an epoxy resin that contains an average oftwo epoxy groups per molecule.) In one embodiment, a mixture ofdifunctional epoxy resins is used, one having an average molecularweight of about 1000 to about 3000, preferably about 1500 to about 2500;and the other having an average molecular weight in excess of about 3000up to about 6000, preferably about 3500 to about 5000.

In one embodiment the difunctional epoxy resin (B-1) is a compoundrepresented by the formula:

wherein in Formula (II), R¹ and R² are independently hydrogen orhydrocarbon groups in the range of 1 to about 20 carbon atoms, and n isa number in the range of 1 to about 20, preferably 1 to about 6, and inone embodiment 1 to about 3, and in another embodiment 1 or 2. Examplesinclude: bisphenol A wherein R¹ and R² are each CH₃; bisphenol F whereinR¹ and R² are each H; bisphenol AD wherein R¹ is H and R² is CH₃. Othersinclude resins wherein: R¹ is H and R² is C₆H₁₃; R¹ is H and R² isC₁₂H₂₅; R¹ is CH₃ and R² is C₂H₅; R¹ is CH₃ and R² is C₄H₉; etc.

The compound (B-2) is at least one compound represented by the formula:

R-(G)_(n)  (I)

In Formula (I) R is an aromatic, alicyclic or heterocyclic group. G is afunctional group selected from the group consisting of COOH, OH, SH,NH₂, NHR¹, (NHC(═NH))_(m)NH₂, R²COOH, R²OH, R²SH, R²NH₂ and R²NHR¹,wherein R¹ is a hydrocarbon group, preferably an alkyl group, of 1 toabout 6 carbon atoms, more preferably 1 to about 3 carbon atoms, and R²is an alkylene or alkylidene group, preferably an alkylene group, of 1to about 6 carbon atoms, more preferably 1, 2 or 3 carbon atoms, and mis a number in the range of 1 to about 4 and in one embodiment m is 2. Gis preferably NH₂, OH or CH₂NH₂. n is a number ranging from 3 up to thenumber of displaceable hydrogens on R.

The aromatic R groups in Formula (I) can be mononuclear, e.g., benzene;polynuclear wherein the aromatic nucleus is of the fused type with thearomatic nucleus being fused at two points to another nucleus, e.g.,naphthalene, or of the linked type wherein at least two nuclei(mononuclear or polynuclear) are linked through bridging linkages toeach other. These bridging linkages can be carbon-to-carbon singlebonds, ether linkages, keto linkages, sulfide linkages, sulfur atoms,sulfinyl linkages, sulfonyl linkages, alkylene linkages, alkylidenelinkages, amino linkages, etc. Normally the aromatic group R is abenzene nucleus. These aromatic groups can be alkyl-substituted aromaticgroups wherein one or more alkyl groups (e.g., C₁-C₁₀) are attached tothe aromatic nucleus.

The alicyclic R group in Formula (I) can be saturated or unsaturated andpreferably has from 3 to 6 carbon atoms, more preferably 5 or 6 carbonatoms. These cyclic groups can be alkyl-substituted alicyclic groupswherein one or more alkyl groups (e.g., C₁-C₁₀) are attached to ringcarbon atoms. Examples include R groups derived from cyclopropane,cyclobutane, cyclopentane, cyclopentene, 1,3-cyclopentadiene,cyclohexane, cyclohexene, 1,3-cyclohexadiene, etc.

The heterocyclic R group in Formula (I) is preferably derived from a 5-or 6-membered ring compound wherein the hetero atom(s) are N, S or O.These cyclic groups can be alkyl-substituted heterocyclic groups whereinone or more alkyl groups (e.g., C₁-C₁₀) are attached to ring carbon or Natoms. Examples include R groups derived from pyrrole, furan, thiophene,pyridine, etc.

Useful examples of compound (B-2) include o-aminophenol, m-aminophenol,p-aminophenol, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 1,3-xylylenediamine, isophoronediamine, 1,3,5-trihydroxybenzene, diaminodiphenylsulfone, 1,4-xylylenediamine,3-aminophenylsulfone, 1,4-cyclohexanediamine, 1,3-cyclohexanediamine,1-o-tolylbiguanide, and mixtures of two or more thereof.

In one embodiment components (B-1) and (B-2) are merely blended witheach other prior to or at the time of mixing with component (A). In thisembodiment components (B-1) and (B-2) are not pre-reacted with eachother. In one embodiment components (B-1) and (B-2) are pre-reacted witheach other prior to being combined with component (A). This reaction canbe effected by contacting component (B-1) with component (B-2) underreaction conditions until the desired product is obtained. In eithercase, the ratio of equivalents of (B-1) to (B-2) is generally from about1:2 to about 1:4, and in one embodiment from about 1:2.5 to about 1:3.5.The weight of an equivalent of component (B-1) is determined by dividingthe molecular weight of component (B-1) by the average number of epoxygroups per molecule in (B-1). The weight of an equivalent of (B-2) isdetermined by dividing the molecular weight of (B-2) by the number offunctional groups, G, per molecule in (B-2). In determining the numberof functional groups in (B-2), COOH, SH, NHR¹, R²COOH, R²SH and R²NHR¹are each counted as one functional group. NH₂ and R²NH₂ are each countedas two functional groups. The number of functional groups in(NHC(═NH))_(m)NH₂ is equal to the number of reactive nitrogen sites inthe group. Thus, for example, when G is NHC(═NH)NHC(═NH)NH₂ it iscounted as 6 functional groups.

When components (B-1) and (B-2) are pre-reacted with each other thereaction temperature is generally from about 60° C. to about 150° C.,and in one embodiment from about 80° C. to about 110° C. The timerequired to complete the reaction is dependent upon the desired degreeof reaction, but is generally from about 2 to about 24 hours, and in oneembodiment from about 4 to about 8 hours. In one embodiment either orboth of components (B-1) and (B-2) are dissolved in a suitable solventprior to being reacted with each other. Examples of such solventsinclude methylisobutylketone, methyl ethyl ketone, benzene, toluene,acetone, tetrahydrofuran, etc.

In one embodiment the above-described epoxy adhesive composition alsocontains an effective amount of a supplemental adduct (C) to enhance thecuring of the epoxy adhesive composition. This supplemental adduct isthe reaction product of at least one difunctional epoxy resin with atleast one alkylene polyamine. The difunctional epoxy resins are the sameas the resins (B-1) discussed above. The alkylene polyamines arecompounds represented by the formula:

wherein in Formula (III), each R¹ is independently hydrogen or ahydrocarbon group, preferably alkyl, of 1 to about 10 carbon atoms,preferably 1 to about 4 carbon atoms; R² is an alkylene group ofpreferably 1 to about 4 carbon atoms, more preferably 2 or 3 carbonatoms; and n is a number in the range of 1 to about 10, preferably 1 toabout 4, more preferably 1 or 2. Examples include ethylene diamine,triethylene tetramine, propylene diamine, trimethylene diamine, etc. Thereaction between the difunctional epoxy resin and the alkylene polyamineis generally carried out at a temperature of from about 25° C. to about100° C., and in one embodiment from about 70° C. to about 90° C. Thetime required to complete the reaction is dependent upon the desireddegree of reaction, but is generally from about 2 to about 24 hours, andin one embodiment from about 2 to about 4 hours. In one embodimenteither or both of the reactants are dissolved in a suitable solventprior to being reacted with each other. Examples of such solventsinclude methylisobutylketone, methylethylketone, benzene, toluene,acetone, tetrahydrofuran, etc.

The above epoxy adhesive compositions preferably comprise from about 10%to about 40% by weight, and in one embodiment about 20% to about 30% byweight of the multifunctional epoxy (A); from about 40% to about 80% byweight, and in one embodiment about 55% to about 75% by weight of thecomposition (B); and up to about 25% by weight, and in one embodimentfrom about 5% to about 15% by weight of the supplemental adduct (C).

In one embodiment the epoxy adhesive compositions contain an effectiveamount of at least one low molecular weight difunctional epoxy compoundto enhance the adhesive characteristics of these compositions. These lowmolecular weight epoxies typically have molecular weights in the rangeof about 160 to about 400, and in one embodiment from about 200 to about250. In one embodiment the low molecular weight epoxy is represented bythe formula:

wherein in Formula (IV), Ar is an aromatic or cycloaliphatic group ofthe type discussed above with respect to Formula (I) with themononuclear groups (e.g., benzene) being preferred, and R¹ and R² areindependently alkylene or alkylidene groups of preferably 1 to about 6carbon atoms, and in one embodiment from 1 to about 3 carbon atoms. Anexample of a useful low molecular weight difunctional epoxy is one inwhich Ar is a benzene nucleus, and R¹ and R² are each methylene; thiscompound being available under the tradename Heloxy 69 from RhonePoulenc. These low molecular weight difunctional epoxies are present inthe adhesive compositions at concentrations of up to about 10% byweight, and in one embodiment up to about 5% by weight.

In one embodiment the epoxy adhesive composition also contains aneffective amount of at least one phenolic resole to enhance the adhesivecharacteristics of these compositions. These resoles are typicallyprovided in diluted form, the diluent being a suitable solvent such asethanol, and having a solids content of, for example, about 50% to about70% by weight. Useful phenolic resoles typically have gel times of about30 to about 200 seconds at 150° C., and in one embodiment about 90 toabout 140 seconds at 150° C. Commercially available phenolic resolesthat are useful include PR-GNF-1 (a product of Sumitomo Durez identifiedas having a 60% by weight solids content in ethanol and a gel time of 90to 140 seconds at 150° C.), and Arofene 536-E-56 (Ashland Chemical). Thephenolic resoles are present in the adhesive compositions atconcentrations of up to about 5% by weight, and in one embodiment up toabout 3% by weight.

When the adhesion-promoting layer is an epoxy or phenolic resin, ormixture of epoxy resins as described above, the thickness of the layermay range from about 1 micron (10,000 Å) in thickness up to about 50microns (500,000 Å), particularly when the coated foil is to belaminated to a paper phenolic board. The thickness of such layers oftenis expressed in grams/meter², and thicknesses of from about 10 to about50 grams/meter² are useful. These thicker layers generally are appliedby roll coating.

The application of the epoxy adhesives described above to the treatmentlayer of the metal body or foil is typically effected at a temperatureof from about 15° C. to about 45° C., more often from about 20° C. toabout 30° C. Following application of the epoxy adhesive to thetreatment layer, the epoxy adhesive is semi-cured (B-staged) by heatingit to a temperature of from about 90° C. to about 180° C., and moreoften from about 140° C. to about 170° C. for preferably about 0.5 toabout 10 minutes to enhance drying of the surface. Generally, drying canbe accomplished in from about 1 to about 5 minutes. The dry film weightof the B-staged epoxy adhesive on the treatment layer may be from about10,000 to 500,000 Å.

The following examples are provided for purposes of illustrating theepoxy resin mixtures useful as adhesives in the adhesion-promotinglayer. Unless otherwise indicated in the following example as well asthroughout the specification and claims, all parts and percentages areby weight, all temperatures are in degrees centigrade, and all pressuresare at or near atmospheric.

EXAMPLES 1-5 Adduct (B-I)

DER 664 (75 g, a product of Dow Chemical identified as a bisphenol Aepoxy resin having an epoxy equivalent weight of about 875-975) isdissolved in 55 grams of methylisobutylketone with heating overnight toprovide an epoxy solution. Meta-aminophenol (9.3 g) is dissolved in 20grams of methylisobutylketone with heating to provide a reagentsolution. The reagent solution is added to the epoxy solution and heatedto 115° C. for 6 hours to provide a product that is 96% reacted based onepoxy titration.

Adduct (B-II)

DER 667 (75 g, a product of Dow Chemical identified as a bisphenol Aepoxy resin having an epoxy equivalent weight of about 1600-2000) isdissolved in 75 grams of methylisobutylketone with heating overnight toprovide an epoxy solution. Meta-aminophenol (4.5 g) is dissolved in 15grams of methylisobutylketone with heating to provide a reagentsolution. The reagent solution is added to the epoxy solution and heatedto 115° C. for 10.5 hours to provide a product that is 90% reacted basedon epoxy titration.

Adducts (B-I) and (B-II) are blended with various multifunctionalepoxies as indicated in Table I below to provide the adhesiveformulations indicated in the table. The multifunctional epoxies thatare used are:

MT 0163 (a product of Ciba Geigy identified as a tetrafunctional epoxyresin);

Tactix 785 (a product of Dow Chemical identified as an epoxy novolac);and

DPS 164 (a product of Shell identified as an epoxy novolac).

TABLE I Example Formulation 1 75% Adduct (B-I) 25% MT 0163 2 75% Adduct(B-I) 25% Tactix 785 3 20% Adduct (B-I) 55% Adduct (B-II) 25% Tactix 7854 25% Adduct (B-I) 50% Adduct (B-II) 25% Tactix 785 5 75% Adduct (B-I)25% DPS 164

Other organic materials which are also useful in the adhesion-promotinglayer include: benzotriazole and its derivatives; metal salts of organicacids such as sodium and potassium citrates; organic amines; cydricalklene ureas; orthoesters; etc. Inorganic adhesion-promoting layers maycomprise phosphorus or chromium-containing compounds.

In another embodiment the adhesion-promoting layers used in the presentinvention may comprise various organometallic compounds such as thosebased on silicon, titanium, zirconium, aluminum, etc.

A variety of titanates useful as adhesion-promoters are availablecommercially such as from Kenrich Petrochemicals, Inc. under the tradedesignation Ken-React®. The types of titanates include: monoalkoxytitanates such as isopropyl tri(N-ethylaminoethylamino) titanate,isopropyl tri-isostearoyl titanate and titanium di(dioctylpyrophosphate)oxyacetate; coordinate titanates such as tetraisopropyldi(dioctylphosphito)titanate; and neoalkoxy titanates such as neoalkoxytri(p-N-(β-aminoethyl)aminophenyl)titanate. Other types include chelate,quaternary and cycloheteroatom titanates.

Zirconium adhesion promoters are also available from Kenrich. Typicalzirconates include neoalkoxy trisneodecanoyl zirconate, neoalkoxytris(dodecanoyl) benzenes sulfonyl zirconate, neoalkoxytris(m-aminophenyl) zirconate, ammonium zirconium carbonate andzirconium propionate.

In one preferred embodiment, the adhesion-promoting layer comprises atleast one organofunctional silane. Any of the silane compoundsconventionally used in preparing PCBs can be used in the presentinvention. In one embodiment, the organofunctional silane may be asilane coupling agent represented by the formula:

R_(4-n)SiX_(n)  (V)

wherein R is an alkyl or aryl group, or a functional group representedby the formula:

C_(x)H_(2x)Y

wherein x is from 0 to 20 and Y is selected from the group consisting ofamino, amido, hydroxy, alkoxy, halo, mercapto, carboxy, acyl, vinyl,allyl, styryl, epoxy, isocyanato, glycidoxy and acryloxy groups, X is ahydrolyzable group, such as alkoxy (e.g., methoxy, ethoxy, etc.),phenoxy, acetoxy, etc., or halogen (e.g., chlorine); and n is 1, 2, 3 or4, and preferably n is 3. The silane coupling agents represented byFormula (V) include halosilanes, aminoalkoxysilanes, aminophenylsilanes,phenylsilanes, heterocyclic silanes, N-heterocyclic silanes, acrylicsilanes and mercapto silanes. Mixtures of two or more silanes also areuseful. In one embodiment X is OR wherein R is an alkyl group containingup to about 5 carbon atoms or an aryl group containing up to about 8carbon atoms. In other embodiments x is an integer from 0 to 10 and moreoften from 1 to about 5.

Examples of silanes wherein R is an alkyl or aryl group includemethyltrimethoxysilane, ethylltrimethoxysilane, phenyltrimethoxysilane,phenyltriacetoxy silane, methyltrimethoxysilane, etc.

Examples of vinyl-containing silanes include vinyltrimethoxysilane,1,3-divinyltetramethyldisilane vinyltriethoxysilane,vinyltriisopropoxysilane, vinyl tris(2-methoxyethoxy) silane andvinyltris (t-butylperoxy) silane.

The silane coupling agent can be an epoxy silane represented by theformula:

wherein: R¹, R² and R³ are independently hydrogen or hydrocarbon groups;R⁴ and R⁵ are independently alkylene or alkylidene groups; and R⁶, R⁷and R⁸ are independently hydrocarbon groups. The hydrocarbon groupspreferably contain 1 to about 10 carbon atoms, more preferably 1 toabout 6 carbon atoms, more preferably 1 to about 4 carbon atoms. Thesehydrocarbon groups are preferably alkyl. The alkylene or alkylidenegroups R⁴ and R⁵ preferably contain from 1 to about 10 carbon atoms,more preferably 1 to about 6 carbon atoms, more preferably 1 to about 4carbon atoms, more preferably 1 or 2 carbon atoms. The alkylene andalkylidene groups can be methylene, ethylene, propylene, etc. Oneexample of such a compound is represented by the formula:

In another embodiment, the silane coupling agent can be an acrylicsilane represented by the formula:

wherein: R¹, R² and R³ are independently hydrogen or hydrocarbon groups;R⁴ is an alkylene or alkylidene group; and R⁵, R⁶ and R⁷ areindependently hydrocarbon groups. The hydrocarbon groups preferablycontain 1 to about 10 carbon atoms, more preferably 1 to about 6 carbonatoms, more preferably 1 to about 4 carbon atoms. These hydrocarbongroups are preferably alkyl (e.g., methyl, ethyl, propyl, etc.). Thealkylene and alkylidene groups preferably contain from 1 to about 10carbon atoms, more preferably 1 to about 6 carbon atoms, more preferably1 to about 4 carbon atoms. The alkylene groups include methylene,ethylene, propylene, etc. An example of such compound is represented bythe formula:

CH₂═C(CH₃)COOCH₂CH₂CH₂Si(OCH₃)₃  (VIIA)

The silane coupling agent also can be an amino silane represented by theformula:

wherein: R¹, R² and R⁴ are independently hydrogen or hydrocarbon groups;R³ and R⁵ are independently alkylene or alkylidene groups; R⁶, R⁷ and R⁸are independently hydrocarbon groups; and n is 0 or 1. The hydrocarbongroups preferably contain 1 to about 10 carbon atoms, more preferably 1to about 6 carbon atoms, more preferably 1 to about 4 carbon atoms.These hydrocarbon groups are preferably alkyl (e.g., methyl, ethyl,propyl, etc.). The alkylene and alkylidene groups preferably containfrom 1 to about 10 carbon atoms, more preferably 1 to about 6 carbonatoms, more preferably 1 to about 4 carbon atoms. The alkylene groupsinclude methylene, ethylene, propylene, etc. Examples of such silanesinclude those represented by the formulae:

H₂NCH₂CH₂CH₂Si(OC₂H₅)  (VIIIA)

H₂NCH₂CH₂NHCH₂CH₂CH₂Si(OCH₃)₃  (VIIIB)

The mercapto silane coupling agents can be represented by the formula:

wherein R¹ is hydrogen or a hydrocarbon group; R² is an alkylene oralkylidene group; and R³, R⁴ and R⁵ are independently hydrocarbongroups. The hydrocarbon groups preferably contain 1 to about 10 carbonatoms, more preferably 1 to about 6 carbon atoms, more preferably 1 toabout 4 carbon atoms. These hydrocarbon groups are preferably alkyl(e.g., methyl, ethyl, propyl, etc.). The alkylene and alkylidene groupspreferably contain from 1 to about 10 carbon atoms, more preferably 1 toabout 6 carbon atoms, more preferably 1 to about 4 carbon atoms. Thesegroups are preferably alkylene (e.g., methylene, ethylene, propylene,etc.). One example of such a compound is:

HSCH₂CH₂CH₂Si(OCH₃)₃  (IXA)

In yet another embodiment, the silane coupling agent can be representedby the formula:

wherein: R¹, R², R³, R⁵ and R⁷ are independently hydrogen or hydrocarbongroups; R⁴, R⁶ and R⁸ are independently alkylene or alkylidene groups;each R⁹ is independently a hydrocarbon group; Ar is an aromatic group;and X is a halogen. The hydrocarbon groups preferably contain 1 to about10 carbon atoms, more preferably 1 to about 6 carbon atoms, morepreferably 1 to about 4 carbon atoms. These hydrocarbon groups arepreferably alkyl (e.g., methyl, ethyl, propyl, etc.). The alkylene andalkylidene groups preferably contain from 1 to about 10 carbon atoms,more preferably 1 to about 6 carbon atoms, more preferably 1 to about 4carbon atoms. These groups are preferably alkylene (e.g., methylene,ethylene, propylene, etc.). The aromatic group Ar can be mononuclear(e.g., phenylene) or polynuclear (e.g., naphthylene) with themononuclear groups and especially phenylene being preferred. Thehalogen, X, is preferably chlorine or bromine, more preferably chlorine.An example of such a silane is represented by the formula:

CH₂═CHC₆H₄CH₂NHCH₂CH₂NH(CH₂)₃Si(OCH₃)₃HCl  (XA)

In yet another embodiment, the silane coupling agent can be representedby the formula:

wherein R¹, R², R³, R⁵, R⁶ and R⁷ are independently hydrocarbon groups;R⁴ is an alkylene or alkylidene group; and n is 0 or 1. The hydrocarbongroups preferably contain 1 to about 10 carbon atoms, more preferably 1to about 6 carbon atoms, more preferably 1 to about 4 carbon atoms.These hydrocarbon groups are preferably alkyl (e.g., methyl, ethyl,propyl, etc.). The allkylene and alkylidene group preferably containsfrom 1 to about 10 carbon atoms, more preferably 1 to about 6 carbonatoms, more preferably 1 to about 4 carbon atoms. This group ispreferably alkylene (e.g., methylene, ethylene, propylene, etc.).Examples of such compounds include tetraethoxy silane and(CH₃O)₃SiCH₂CH₂Si(OCH₃)₃.

In one preferred embodiment, the silane coupling agents include thoseselected from the group consisting of aminopropyltrimethoxy silane,tetraethoxy silane, bis(2-hydroxyethyl)-3-aminopropyltriethoxy silane,3-(N-styrylmethyl-2-aminoethylamine) propyltrimethoxy silane,3-glycidoxypropyltrimethoxy silane, N-methylaminopropyltrimethoxysilane, 2-(2-aminoethyl-3-aminopropyl)trimethoxy silane, andN-phenylaminopropyltrimethoxy silane, and mixtures thereof.

A useful silane coupling agent mixture is 3-glycidoxypropyltrimethoxysilane and phenyltriethoxy silane. The weight ratio of the former to thelatter preferably ranges from about 1:10 to about 10:1, more preferablyabout 1:5 to about 5:1, and in one embodiment the weight ratio is about1:3.

Another useful silane mixture is 3-glycidoxypropyltrimethoxy silane andtetraethoxy silane in a weight ratio of from about 1:5 to about 5:1. Inone preferred embodiment the weight ratio is about 1:1.

Another useful silane coupling agent mixture isN-methylaminopropyltrimethoxy silane and chloropropyltrimethoxy silane.The weight ratio of the former to the latter preferably ranges fromabout 1:10 to about 10:1, more preferably about 1:5 to about 5:1, and inone embodiment the weight ratio is about 1:1.

Another useful silane coupling agent mixture is3-(N-styrylmethyl-2-aminoethyl amino)propyltrimethoxy silane andN-methylaminopropyltrimethoxy silane. The weight ratio of the former tothe latter preferably ranges from about 1:10 to about 10:1, morepreferably about 1:5 to about 5:1, and in one embodiment the weightratio is about 1:1.

Yet another useful silane coupling agent mixture is3-glycidoxypropyltrimethoxy silane and N-methylaminopropyltrimethoxysilane. The weight ratio of the former to the latter preferably rangesfrom about 1:10 to about 10:1, more preferably about 1:5 to about 5:1,and in one embodiment the weight ratio is about 1:3.

The adhesion-promoting layers present on the metal bodies and foils ofthe present invention may be applied to the bodies and foils after thevapor-deposited treatment layer using known application methods whichinclude reverse roller coating, doctorblade coating, dipping, painting,spraying, brushing, electrode-position, vapor deposition, etc. Theadhesion-promoting material which can be applied by any of theseprocedures may be neat or dispersed or dissolved in a suitable medium.The process of applying the adhesion-promoting materials may berepeated, if desired, several times.

The organofunctional silane compounds generally are applied in asuitable medium to the vapor-deposited treatment surface. Morespecifically, the silane coupling agents can be applied to the treatmentlayer in the form of a solution in water, a mixture of water andalcohol, or a suitable organic solvent, or as an aqueous emulsion of thesilane coupling agent, or as an aqueous emulsion of a solution of thesilane coupling agent in a suitable organic solvent. Conventionalorganic solvents may be used for the silane coupling agent and include,for example, alcohols, ethers, ketones, and mixtures of these withaliphatic or aromatic hydrocarbons or with amides such asN,N-dimethylformamide. Useful solvents are those having good wetting anddrying properties and include, for example, water, ethanol, isopropanol,and methylethylketone. Aqueous emulsions of the silane coupling agentmay be formed in conventional manner using conventional dispersants andsurfactants, including non-ionic dispersants. It may be convenient tocontact the metal surface with an aqueous emulsion of the silanecoupling agent. The concentration of the silane coupling agent in suchsolutions or emulsions can be up to about 100% by weight of the silanecoupling agent, but preferably is in the range of about 0.1% to about 5%by weight, more preferably about 0.3% to about 1% by weight. The processof coating with the silane coupling agent may be repeated, if desired,several times. However, a single coating step gives generally usefulresults.

The application of the silane coupling agent to the treatment layer istypically effected at a temperature of about 15° C. to about 45° C.,more preferably about 20° C. to about 30° C. Following application ofthe silane coupling agent, it can be heated to a temperature of about60° C. to about 170° C., preferably about 90° C. to 150° C., for about0.1 to about 5 minutes, more often from about 0.2 to about 2 minutes toenhance drying of the surface. The dry film thickness of the silanecoupling agent layer is generally from about 4 to about 200 Å, moreoften about 5 to 40 Å.

Embodiments of the inventive metal foils containing at least onevapor-deposited treatment layer and at least one adhesion-promotinglayer over the treatment layer are illustrated in FIGS. 1-4. FIG. 1illustrates a metal foil 10 of the present invention which comprisesmetal foil 11, a vapor-deposited layer 12 overlaying the metal foil, andan adhesion-promoting layer 13 overlaying the vapor-deposited layer 12.

FIG. 2 illustrates another embodiment of the metal foil 20 of theinvention which comprises the metal foil 21, a vapor-deposited layer 22overlaying one side of the metal foil 21, an adhesion-promoting layer 24overlying the vapor-deposited layer 22, and a second vapor-depositedlayer 23 on the other side of the metal foil 21. When the metal foil 21in FIG. 2 is an electrodeposited metal foil having a shiny side and amatted side, the vapor-deposited layer 22 generally will overlay thematte side of the metal foil, and the vapor-deposited layer 23 willoverlay the shiny side.

FIG. 3 illustrates yet another embodiment of the metal foil 30 of theinvention wherein the foil has a vapor-deposited layer and anadhesion-promoting layer on both sides of the foil. In particular, foil31 is coated on one side with vapor-deposited layer 32 and on the otherside with vapor-deposited layer 33. Adhesion-promoting layers 34 and 35overlay and adhere to the vapor-deposited layers 33 and 32,respectively.

FIG. 4 illustrates another metal foil 40 of the invention wherein twovapor-deposited treatment layers are applied to one side of the metalfoil. In particular, the metal foil 41 is coated on one side withvapor-deposited layer 43, and then a second vapor-deposited layer 44 isapplied over and adheres to vapor-deposited layer 43. A third layer ofvapor-deposited material 42 is applied to the other side of the foil 41.Finally, adhesion-promoting layers 45 and 46 overlay and adhere to thevapor-deposited treatment layers 44 and 42, respectively.

Another embodiment of the invention (not shown in the Figures) comprisesa copper foil having an electrodeposited-metal coating on both sides ofthe foil, a vapor-deposited metal coating on the electrodeposited metalcoating on the matte side, and an adhesion-promoting silane layeroverlying and adhered to the vapor-deposited layer.

The following examples illustrate methods of preparing the metal foilsof the invention.

EXAMPLES A-I

A 1-ounce/ft² standard profile electrodeposited copper foil is cleanedand microetched by dipping in an aqueous acidic solution containing 20%sulfuric and 1% hydrogen peroxide at 65° C. for about 10 seconds. Thefoil is then rinsed with deionized water and dried. Chips or a foil ofthe metal to be deposited are placed on a tungsten or molybdenum boat inthe Edwards apparatus described above, and the cleaned and microetchedcopper foil is placed about 5 inches above the evaporation source insidea Bell jar, and the vacuum is reduced to about 10⁻⁴ millibar or lowerbefore evaporation proceeds. The metal is evaporated at a fixed currentfor between about 0.5 to about 40 minutes. After the vapor depositionprocess is completed, the sample is taken out of the apparatus forevaluation.

An aqueous solution containing 0.25% w of3-glycidoxypropyltrimethoxysilane and 0.25% w of tetraethoxysilane isprepared, and the foil having the vapor-deposited layer is coated onboth sides by dipping in the solution for 30 seconds. After removingexcess solution, the silane-coated foil is then oven-cured for about 1minute at about 90° C. In some of the examples, the microetched foil isdipped in an aqueous acidic solution containing chromium oxide (CrO₃) toprovide a chromium coating either prior to vapor depositing the metal onthe foil or subsequent to vapor depositing the metal on the foil. Thedetails of Examples A-I are summarized in the following Table I.

TABLE I Standard Profile Raw Foil Matte Side Vapor Deposited LayerChromium Current Time Example Dip Metal (mA) (min) A No Al 50-65 4-6  BNo Zn 35-50 4-10 C No Mn 50-65 4-6  D No In 50-65 6-20 E Yes* In 50-656-20 F No Sn 50-65 6-20 G No Ag 35-50 6-15 H No Co 65-80 0.5-4   I No Ni65-80 0.5-4   *Chrome dip after vapor deposition.

EXAMPLES J-S

The general procedure of Examples A-J is repeated except that the rawfoil is a controlled low profile electrodeposited copper foil (1ounce/ft²) having a substantially uniform randomly oriented grainstructure that is essentially columnar grain-free and twin-boundary freeand has an average grain size of up to about 10 microns. In addition, asindicated in the following Table II, the vapor-deposited layer is coatedwith either 3-glycidoxypropyltrimethoxysilane (Silane-1) or a mixture inwater of 0.25% by weight of 3-glycidyloxypropyltrimethoxysilane and0.25% by weight of tetraethoxysilane (Mixture-1). The metal is depositedon the matte side of the foil. The details of Examples J-S aresummarized in the following Table II.

TABLE II Controlled Low Profile Foil Matte Side Vapor Deposited LayerCurrent Time Example Metal (mA) (min) Silane Treatment J Mg 35-50 10-30Silane-1 K Mg 35-50 10-30 Mixture-1 L Ti 65-80 4-6 Silane-1 M Ti 65-804-6 Mixture-1 N Cr 65-80 4-6 Silane-1 O Cr 65-80 4-6 Mixture P Mn 50-654-6 Silane-1 Q Mn 50-65 4-6 Mixture-1 R In 50-65 6-20 Silane-1 S In50-65 6-20 Mixture-1

EXAMPLES T-W

The procedure utilized in these examples is similar to the procedure ofExamples J-S with the exception that the metal is vapor-deposited on theshiny side of the copper foil. Details of Examples T-W are summarized inthe following Table III.

TABLE III Controlled Low Profile Foil Shiny Side Vapor Deposited LayerCurrent Time Example Metal (mA) (min) Silane Treatment T Al 50-65 2-6Mixture-1 U Mg 35-50 2-6 Mixture-1 V Zn 35-50 2-6 Mixture-1 W In 50-652-6 Mixture-1

The metal foils of the present invention having at least onevapor-deposited treatment layer overlying and adhered to at least oneside of the foil, and a layer of adhesion-promoting material overlyingand adhering to at least one treatment layer are particularly useful forforming laminates by bonding the treated copper foils to dielectricsubstrates. Such laminates provide dimensional and structural stabilityto the treated copper foils. The combination of the vapor depositedtreatment layer and the adhesion-promoting layer on the foil enhancesthe bond and peel strength between the copper foil and the dielectricsubstrate. One advantage of the metallic foils of the present inventionhaving the vapor-deposited treatment layer and the adhesion-promotinglayer is that satisfactory bond and peel strength can be obtainedwithout having to provide added surface roughening of the foil prior toapplication of the vapor-deposited treatment layer. Even though themetallic foils may have a standard profile surface, a low-profilesurface or even a very low-profile surface, desirable peel strengths areobtained as a result of the presence of the vapor-deposited treatmentlayer and adhesion-promoting layer. With the foils of the invention,either the matte side or the shiny side can be effectively bonded to adielectric substrate.

Useful dielectric substrates may be prepared by impregnating woven glassreinforcement materials with partially cured resins, usually epoxyresins (e.g., difunctional, tetrafunctional and multifunctionalepoxies). Other useful resins include amino type resins produced fromthe reaction of formaldehyde and urea or formaldehyde and melamine,polyesters, phenolics, silicones, polyamides, polyimides, di-allylphthlates, phenylsilanes, polybenzimidazoles, diphenyloxides,polytetrafluoro-ethylenes, cyanate esters, and the like. Thesedielectric substrates are sometimes referred to as prepregs.

In preparing the laminates, it is useful for both the prepreg materialand the copper foil to be provided in the form of long webs of materialrolled up in rolls. In one embodiment these long webs of foil andprepreg are laminated using a continuous process. In this process acontinuous web of the inventive foil with the vapor-deposited treatmentlayer(s) and adhesion-promoting layer(s) adhered thereto is brought intocontact with a continuous web of prepreg material with the adhesivelayer of the foil contacting the prepreg material under laminatingconditions to form a laminate structure. This laminate structure is thencut into rectangular sheets and the rectangular sheets are then laid-upor assembled in stacks of assemblages.

In one embodiment the long webs of foil and prepreg material are firstcut into rectangular sheets and then subjected to lamination. In thisprocess rectangular sheets of the inventive foil and rectangular sheetsof the prepreg material are then laid-up or assembled in stacks ofassemblages.

Each assemblage may comprise a prepreg sheet with a sheet of foil oneither side thereof, and in each instance, the side (or one of thesides) of the copper foil sheet with the adhesion-promoting layeradhered thereto is positioned adjacent the prepreg. The assemblage maybe subjected to conventional laminating temperatures and pressuresbetween the plates of laminating presses to prepare laminates comprisingsandwiches of a sheet of prepreg between sheets of copper foil.

The prepregs may consist of a woven glass reinforcement fabricimpregnated with a partially cured two-stage resin. By application ofheat and pressure, the copper foil is pressed tightly against theprepreg and the temperature to which the assemblage is subjectedactivates the resin to cause curing, that is crosslinking of the resinand thus tight bonding of the foil to the prepreg dielectric substrate.Generally speaking, the laminating operation will involve pressures inthe range of from about 200 to about 750 psi, more often 200 to 500 psi,temperatures in the range of from about 70° C. to 400° C., more oftenabout 70° C. to about 200° C., and a laminating cycle of from about afew minutes to about 2 hours. The finished laminate may then be utilizedto prepare printed circuit boards (PCB).

In one embodiment, the laminate is subjected to a subtractive copperetching process to form electrically conductive lines or an electricallyconductive pattern as part of a process for making a multilayeredcircuit board. A second adhesion-promoting layer is then applied overthe etched pattern using the techniques discussed above and then asecond prepreg is adhered to the etched pattern; the secondadhesion-promoting layer being positioned between and adhered to boththe etched pattern and the second prepreg. The techniques for makingmultilayered circuit boards are well known in the art. Similarly,subtractive etching processes are well known, an example of which isdisclosed in U.S. Pat. No. 5,017,271, which is incorporated herein byreference.

Laminates obtained by bonding the metal foils of the present inventionto a dielectric substrate are illustrated in FIGS. 5 and 6. The laminate50 of FIG. 5 comprises a metal foil 51 having a vapor-depositedtreatment layer 52 overlaying and adhered to one side of the metal foil51 and a second vapor-deposited treatment layer 53 overlaying andadhering to the other side of the metal foil 51. An adhesion-promotinglayer 54 overlays and is adhered to the vapor-deposited treatment layer52 and a dielectric substrate 55 is bonded to the treatment layer 52.

The structure illustrated in FIG. 6 is identical to the structureillustrated in FIG. 4 with the exception that the foil 60 of FIG. 6contains an additional adhesion-promoting layer 65. Thus, FIG. 6illustrates a metal foil 60 of the invention which comprises a metallicfoil 61 having a vapor-deposited treatment layer 63 on one side and avapor-deposited treatment layer 62 on the other side of the metallicfoil 61. Adhesion-promoting layers 64 and 65 overlay and adhere to thevapor-deposited treatment layers 63 and 62, respectively. A dielectricsubstrate 66 overlays and is bonded to the adhesion-promoting layer 64.

A number of manufacturing methods are available for preparing PCBs fromlaminates. Additionally, there is a myriad of possible end useapplications including radios, televisions, computers, etc., for thePCB's. These methods and end uses are known in the art.

An advantage of the present invention is that the vapor-depositedtreatment layer(s) and the adhesion-promoting layer(s) not only enhanceadhesion, they also provides enhanced oxidation resistancecharacteristics to the treated foil particularly when a vapor-depositedlayer overlays the shiny side of an electrodeposited copper foil. Thislatter characteristic is of particular value due to the fact that thetrend in the industry is for faster and hotter processing practices.Another advantage is that the vapor-deposited treatment layer and theadhesion-promoting layer provide enhanced acid undercutting resistanceto the treated foils.

The improved adhesion exhibited between the copper foils of the presentinvention and the polymeric substrates such as multifunctional epoxyprepregs and difunctional epoxy prepregs is demonstrated by laminatingsome of the treated copper foils of Examples described above to aprepreg, and thereafter evaluating the laminate for initial peelstrength in pounds/inch using the standard Peel Strength Test of IPCTM-650. For comparison, each of the unreacted (raw) foils also islaminated to the prepregs and evaluated. The results of some of thesetests are summarized in the following Table IV.

In Table IV, the examples indicated as control examples correspond tothe referred-to example except that the silane adhesion-promoting layerwas not applied over the vapor-deposited layer prior to lamination. Forexample, the Control-A example is a laminate comprising the foil layer,a vapor-deposited aluminum layer and the indicated prepreg bonded to thealuminum layer. The Example A laminate comprises the copper foil, analuminum layer, a silane layer over the aluminum layer and the prepregover the silane layer.

TABLE IV Peel Strength Test Results Initial Peel Strength (lb/in) Foilof Multifunctional Difunctional Example Epoxy Prepreg Epoxy Prepreg A 111.6 Control A NA¹ 11.7 B 10.1 11.1 Control B 5.3 5.8 C 10.8 NA ControlC 4.6 NA D 10.5 10.8 Control D 7.3 6.2 E 10.8 11.8 Control E 8.4 9.6 F9.4 NA Control F 7.8 NA H 11.0 NA Control H 4.4 NA J 1.7 NA Control J0.4 NA K 5.2 NA Control K 0.4 NA L 6.4 NA Control L 2.6 NA M 5.8 NAControl M 2.6 NA T 5.4 7.1 Control T 5.0 7.3 V 4.8 7.0 Control V 1.2 4.7W 5.4 5.3 Control W 1.8 2.7 Untreated Foil Comparisons Standard Foil²2.8 5.9 (matte side) Low Profile Foil³ 0.4 NA (matte side) Low ProfileFoil⁴ 0.2 1.9 (shiny side) ¹NA = not available. ²As used in ExamplesA-I. ³As used in Examples J-S. ⁴As used in Examples T-W.

While the invention has been explained in relation to its preferredembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims.

What is claimed is:
 1. A process for treating a copper foil to enhanceadhesion to laminating materials, comprising: vapor depositing at leastone metallic treatment layer on at least one side of an untreated copperfoil; and applying at least one layer of at least one adhesion-promotingmaterial over and adhered to said treatment layer, saidadhesion-promoting material being suitable for enhancing adhesionbetween said foil and laminating materials; wherein the metal in thevapor-deposited metallic treatment layer is selected from the groupconsisting of magnesium, aluminum, titanium, chromium, manganese,copper, bismuth, cobalt, nickel, zinc, indium, tin, molybdenum, silver,gold, tungsten, zirconium, antimony, chromium-zinc alloys, brass,bronze, and mixtures or alloys thereof, wherein said adhesion promotingmaterial is at least one selected from multifunctional epoxy resins andorganofunctional silanes.
 2. The process of claim 1 wherein the foil isan electrodeposited copper foil.
 3. The process of claim 2 wherein thecopper foil is a controlled low profile electrodeposited copper foilhaving a substantially uniform randomly oriented grain structure that isessentially columnar grain free and twin boundary free and has anaverage grain size of up to about 10 microns.
 4. The process of claim 2wherein the copper foil is a standard profile electrodeposited copperfoil having a columnar grain structure of preferred orientation andcrystal defects including discolorations and twin boundaries and havingan average grain size of up to about 20 microns.
 5. The process of claim1 wherein the foil is a wrought copper foil.
 6. The process of claim 1wherein the foil is an as-plated or annealed electrodeposited copperfoil.
 7. The process of claim 1 wherein the foil is an as-rolled orannealed wrought copper foil.
 8. The process of claim 1 wherein saidtreatment layer is vapor-deposited on both sides of the foil.
 9. Theprocess of claim 1 wherein said treatment layer is vapor-deposited onboth sides of the foil and said adhesion-promoting material is depositedon the treatment layer on both sides of the foil.
 10. The process ofclaim 1 wherein the foil is an electrodeposited copper foil having ashiny side and a matte side, and said treatment layer is vapor-depositedon the matte side of the copper foil.
 11. The process of claim 10wherein the metal of the treatment layer on the matte side is selectedfrom the group consisting of indium, tin, cobalt, nickel, copper,manganese, chromium titanium, bismuth, zinc, and zinc-chromium alloys,and mixtures of two or more of said metals.
 12. The process of claim 10wherein a metallic treatment layer is vapor-deposited on the shiny sideof the copper foil, and the metal of said metallic treatment layer onthe shiny side is selected from the group consisting of indium,magnesium, aluminum, copper, zinc, chromium, tin, nickel, cobalt andzinc-chromium alloys, and mixtures of two or more of said metals. 13.The process of claim 1 wherein the adhesion-promoting material isapplied by vapor deposition.
 14. The process of claim 1, wherein themetallic treatment layer is deposited by sputtering.
 15. The process ofclaim 1 wherein the adhesion-promoting material is a multifunctionalepoxy compound selected from the group consisting of trifunctionalepoxies, tetrafunctional epoxies and epoxy novolacs, and mixturesthereof.
 16. The process of claim 1 wherein the adhesion-promotingmaterial comprises a mixture of epoxy resins comprising (A) at least onemultifunctional epoxy resin; and (B) a composition derived from (B-1) atleast one difunctional epoxy resin; and (B-2) at least one componentrepresented by the formula: R--(G)_(n)  (I) wherein in Formula I, R isan aromatic, alicyclic or heterocyclic group; G is a functional groupselected from the group consisting of COOH, OH, SH, NH₂NHR¹,(NHC(═NH))_(m)NH₂, R²COOH, R²OH, R²SH, R²NH₂ and R²NHR¹, wherein R¹ as ahydrocarbon, R² is an alkylene or alkylidene group, and m is a number inthe range of from 1 to about 4; and n is a number ranging from 3 up tothe number of displaceable hydrogens on R.
 17. The process of claim 1wherein the adhesion-promoting material is at least one organofunctionalsilane compound represented by the formula: R_(4-n)SiX_(n) wherein R isan alkyl or aryl group or a functional group represented by the formulaC_(x)H_(2x)Y wherein x is from 0 to 20 and Y is selected from the groupconsisting of amino, amido, hydroxy, alkoxy, halo, mercapto, carboxy,aryl, vinyl, allyl, styryl, epoxy, isocyanate, glycidoxy, and acryloxygroups, X is a hydrolyzable group; and n is 1, 2, 3 or
 4. 18. Theprocess of claim 1 wherein the thickness of said vapor depositedtreatment layer is from about 10 Å to about 3000 Å.
 19. The process ofclaim 1 wherein the adhesion-promoting material is at least one epoxysilane represented by the formula:

wherein R¹, R² and R³ are independently hydrogen or hydrocarbon groups;R⁴ and R⁵ are independently alkylene or alkylidene groups; and R⁶, R⁷and R⁸ are independently hydrocarbon groups.
 20. The process of claim 1wherein said treatment layer is subjected to an elevated temperature offrom about 80° C. to about 800° C. prior to application of theadhesion-promoting material.
 21. The process of claim 1 wherein twotreatment layers are vapor-deposited on at least one side of the foil,each treatment layer comprising a different metal.